The thermosyphon with adiabatic vacuum chamber in this study were made from a copper tube with inner diameter and outer diameter was 20.60 mm and 22.22 mm, respectively. Evaporator length of 150 mm, 300 mm and 400 mm. Three sections length (evaporator, adiabatic, condenser) were equal. The vacuum chamber (vacuum range:20-25 inHg), which surrounds adiabatic section, had diameter 50 mm, 60 mm and 75 mm (see in Figure 2).
Working fluid was used R-134a, ethanol and distilled water with filling ratio 50% by evaporator volume. Tested on various inclined angle as 30, 60, 70, 80 and 90o by reference with horizontal axis. Outside of thermosyphon was perfectly insulated. Water was used as heating and cooling. Thermocouple (Type K. accuracy ±0.5 oC) were used for temperature measurement, that installed 3 points on the outer thermosyphon tube in each section and moreover installed 2 points on outer wall of vacuum chamber, 4